1. Field of the Invention
This invention relates to improved methods for the long-term treatment of wastewater and contaminated groundwater, especially contaminated groundwater from persistent sources, using self-regulating bacterial treatment requiring minimal maintenance.
2. Background and Prior Art
Persistent contamination of wastewater and groundwater presents an ongoing problem because any treatment method must be established and maintained for extended time-periods when compared to sites no longer producing contaminants. Abandoned mines leak acids and acid soluble minerals continuously and effective closure is cost prohibitive. Coal yards/piles at operating coal fired power plants are a significant point source for contamination and the leakage is expected to be continuous until the power plant is closed. Active pump and treat technologies require resources such as power, treatment chemicals and personnel. These costs cannot be incorporated into product pricing under any economically sound scenario.
On site and in situ bioremediation schemes offer promise of lower cost and acceptable thoroughness but systems attempted to date have not found general acceptance. Examples of such treatment methods may be found in U.S. Pat. No. 5,076,927 to Hunter; U.S. Pat. No. 5,514,279 to Blowes, U.S. Pat. No. 5,772,887 to Noah et al.; U.S. Pat. No. 5,833,855 to Saunders; U.S. Pat. No. 5,922,204 to Hunter; and U.S. Pat. No. 6,398,960 to Borden. A survey of technologies particularly adapted to mine drainage is Handbook of Technologies for Avoidance and Remediation of Acid Mine Drainage, Skousen et al. eds., National Mine Land Reclamation Ctr., Morgantown, 1988.
The technologies proposed in the above-identified references are difficult to regulate on an on-going basis due to outflow seepage, plugging, and difficulty in regulating the operational rate of the treatment method. The need exists, therefore, for a treatment system which is stable, effective for the contaminants to be treated, does not require frequent attention, easily replenished and easily cleaned of solid debris. It is particularly desirable that the system has little or no power requirement and that once established will be operable for multiple years if not indefinitely.